This application is directed to an image forming apparatus, a system and method of predicting a photoreceptor replacement interval.
Devices such as printers, copiers, and fax machines often use a photoreceptor (also known as a photoconductor) having a photoreceptor charge transport layer. One type of photoreceptor is known as a photoreceptor drum (also know as a photoconductor drum). As the photoreceptor drum is used, the thickness of the photoreceptor charge transport layer is reduced. There comes a time when, at a certain thickness point, the photoreceptor charge transport layer becomes thin enough that it will no longer support latent image production and, therefore, the charge transport layer of the photoreceptor is considered to have failed. In view of this, manufacturers of photoreceptor devices generally provide users with a fixed interval setting to replace the photoreceptor in the device. This fixed interval setting is set by the manufacturer for an entire population of a particular type of photoreceptor. This fixed interval setting is intended to ensure that the photoreceptor is replaced prior to the charge transport layer becoming reduced enough so as not to support image reproduction. A difficulty is that this fixed interval setting does not take into consideration the manner or environment in which a user actually uses the device having the photoreceptor. Replacing the photoreceptor at a fixed interval typically results in more frequent replacement of the photoreceptor than what is required for individual use of a device.
Instead of replacing the photoreceptor at a fixed interval, it has been considered that in-situ determination of the photoreceptor charge transport layer thickness could be made and used to predict failure of a photoreceptor. Predicting failure of the photoreceptor charge transport layer on an individual basis eliminates the need for replacing the photoreceptor at a predetermined interval, for example, while a particular photoreceptor still has a remaining useful life based on the thickness of the photoreceptor charge transport layer. Performing a predictive calculation based on the use of an individual photoreceptor enables a user to reduce the cost of operating a device having the photoreceptor by running each photoreceptor to a point at which the photoreceptor charge transport layer is just about to fail.
Some effort has been expended to enable in-situ determination of photoreceptor charge transport layer thickness for devices that use bias charged roll chargers. This effort is based on key characteristic behaviors of bias charged roll chargers, and in particular, the saturation of the photoreceptor voltage at the characteristic “knee” of the charge curve.
Many marking engines use non-contact charging of the photoreceptor. One type of non-contact charging is scorotron charging, which uses corona discharge to generate ions that are directed to a surface of the photoreceptor charge transport layer. A scorotron usually includes coronode wires with a scorotron grid formed by a metal mesh or screen placed between the coronode wires and the surface of the photoreceptor charge transport layer. The scorotron grid is biased to a potential close to that desired at the surface of the photoreceptor charge transport layer. When the surface potential of the photoreceptor charge transport layer reaches the potential of the scorotron grid bias, the photoreceptor charging process ceases.
The key characteristic behaviors of bias charged roll chargers are completely inapplicable for photoreceptor devices that use non-contact charging.
A method of predicting the photoreceptor replacement interval in photoreceptor devices that use a scorotron charge device is disclosed in U.S. patent application Ser. No. 12/647,908. However, that disclosed method makes several assumptions regarding variables that affect the photoreceptor thickness estimation. For example, in U.S. patent application Ser. No. 12/647,908, an initial voltage of the photoreceptor charge transport layer and a slope of the scorotron charge device are assumed to be known constants.